56 research outputs found
Pointlike constituent quarks and scattering equivalences
In this paper scattering equivalences are used to simplify current operators
in constituent quark models. The simplicity of the method is illustrated by
applying it to a relativistic constituent quark model that fits the meson mass
spectrum. This model requires a non-trivial constituent quark current operator
to fit the pion form factor data. A model with a different confining
interaction, that has the identical spectrum and can reproduce the measured
pion form factor using only point-like constituent quark impulse currents is
constructed. Both the original and transformed models are relativistic
direct-interaction models with a light-front kinematic subgroup.Comment: 12 pages, 6 figures, corrected caption on fig
On the reliability of the theoretical internal conversion coefficients
Possible sources of uncertainties in the calculations of the internal
conversion coefficients are studied. The uncertainties induced by them are
estimated.Comment: 16 pages (including 3 figures inserted by 'epsfig' macro
Finite size and intrinsic field effect on the polar-active properties of the ferroelectric-semiconductor heterostructures
Using Landau-Ginzburg-Devonshire approach we calculated the equilibrium
distributions of electric field, polarization and space charge in the
ferroelectric-semiconductor heterostructures containing proper or incipient
ferroelectric thin films. The role of the polarization gradient and intrinsic
surface energy, interface dipoles and free charges on polarization dynamics are
specifically explored. The intrinsic field effects, which originated at the
ferroelectric-semiconductor interface, lead to the surface band bending and
result into the formation of depletion space-charge layer near the
semiconductor surface. During the local polarization reversal (caused by the
inhomogeneous electric field induced by the nanosized tip of the Scanning Probe
Microscope (SPM) probe) the thickness and charge of the interface layer
drastically changes, it particular the sign of the screening carriers is
determined by the polarization direction. Obtained analytical solutions could
be extended to analyze polarization-mediated electronic transport.Comment: 35 pages, 12 figures, 1 table, 2 appendices, to be submitted to Phys.
Rev.
Elastic Charge Form Factors of and K Mesons
The elastic charge form factors of the charged and mesons are
calculated in modified impulse approximation using instant form of relativistic
Hamiltonian dynamics. Our approach gives pion and kaon electromagnetic form
factors in the large range of momentum transfer. The results are in good
agreement with the available data. Relativistic effects are large at all values
of momentum transfers. The pion and kaon form factors at large depend
strongly on the choice of model. The experiments on pion form factor at large
momentum transfer planned at CEBAF will choose between such models. In the case
of kaon such a choosing may be performed only if supplemented by accurate
measurements of kaon MSR.Comment: 9 pages, LaTeX, 2 uuencoded PostScript figure
Form factors in RQM approaches: constraints from space-time translations
Different relativistic quantum mechanics approaches have recently been used
to calculate properties of various systems, form factors in particular. It is
known that predictions, which most often rely on a single-particle current
approximation, can lead to predictions with a very large range. It was shown
that accounting for constraints related to space-time translations could
considerably reduce this range. It is shown here that predictions can be made
identical for a large range of cases. These ones include the following
approaches: instant form, front form, and "point-form" in arbitrary momentum
configurations and a dispersion-relation approach which can be considered as
the approach which the other ones should converge to. This important result
supposes both an implementation of the above constraints and an appropriate
single-particle-like current. The change of variables that allows one to
establish the equivalence of the approaches is given. Some points are
illustrated with numerical results for the ground state of a system consisting
of scalar particles.Comment: 37 pages, 7 figures; further comments in ps 16 and 19; further
references; modified presentation of some formulas; corrected misprint
Finite Size and Intrinsic Field Effect on the Polar-Active Properties of Ferroelectric-Semiconductor Heterostructures
Using Landau-Ginzburg-Devonshire approach we calculated the equilibrium distributions of electric field, polarization, and space charge in the ferroelectric-semiconductor heterostructures containing proper or incipient ferroelectric thin films. The role of the polarization gradient and intrinsic surface energy, interface dipoles, and free charges on polarization dynamics are specifically explored. The intrinsic field effects, which originated at the ferroelectric-semiconductor interface, lead to the surface band bending and result into the formation of depletion space-charge layer near the semiconductor surface. During the local polarization reversal (caused by the electric field of the nanosized tip of the scanning probe microscope) the thickness and charge of the interface layer drastically changes, in particular, the sign of the screening carriers is determined by the polarization direction. Obtained analytical solutions could be extended to analyze polarization-mediated electronic transport. © 2010 The American Physical Society.Authors are grateful to E. Tsymbal and E. Tsymbal for valuable critical remarks. Research is sponsored by Ministry of Science and Education of Ukraine and National Science Foundation(Materials World Network, Grant No. DMR-0908718). S.V.K. and A.B. acknowledge the DOE SISGR program. P.M. is supported by the Division of Scientific User Facilities, US DOE
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